Winl ield scott



Patented Aug. 9, 1927.

UNITED STATES rATENT OFFICE WINBIEIJD SCOTT, F AKRON, OHIO, ASSIGNOR TO E. I. DU FONT DE NEMOURS & COM- PANY, OF WILMINGTON, DELAWARE, A CORPORATION OF DELAWARE.

VULGANIZATION OF RUBBER.

1T0 Drawing. Original application filed December 19, 1922, Serial No 607,883. Divided and this application filed April 23, 1924;. Serial No. 708,336.

This invention relates to the vulcanization of rubber, gutta percha, and the like, and

comprises a process of vulcanizing in which there is used as an accelerator the formaldehyde derivative of the condensation product of an amine (for example. a primary aromatic amine) and a straight chain aldehyde.

This application is a division of my application, Serial No. 607,883 filed Dec. 19, 1922. i

The reaction mixture of equimolecular proportions of acetaldehyde and aniline is a sticky, viscous oil that soon turns a dark red on exposure to the air. Upon drying in air or on long storage this syrupy material decomposes to some extent, becoming rather dark in color, with thetormation of phenylcarbylamine.

By using an excess of acetaldehyde, e. g. 1 or 2 moles for each mole of aniline, a more viscous product is obtained, which upon drying in air, becomes quite dark in color, due to a slight decomposition. This material is a soft resin, and almost/black in color.

react with condensation products of aromatic. ammes and stralght chain aldehydes havmg more than one carbon atom, to form substances of complex molecular structure which are harder, and are more readily handled, than the original condensation products, and possess at least as goodaccelerating power. Thus I have found that formaldehyde will. further react with the product obtained from the reactionof aniline and an excess of r acetaldehyde to form a material of a hard 0 to brown, whereasthe resin obtained from aniline and acetaldehyde alone, when ground It readily softens from the heat of the hand and is rather sticky when warms diamine or of anhydroformaldehyde-aniline on the condensation product of acetaldehyde and aniline. Neither is the reaction product of aniline and a mixture of acetaldehyde and formaldehyde the same as that mentioned above. A mixture of formaldehyde and acetaldchyde reacts with aniline to form the Schi'ffs bases of the respective aldehydes.

The reaction product oi? acetaldehyde and aniline which has been resinified by formaldehyde has several distinctadvantages over ethvlidene-aniline as an accelerator of vulcanization. The resinous material is easily handled, weighed and removed from containers; ethylidene-aniline a special effort must be made to'remove all the material from pans or containers into'which it is weighed be fore the milling operation. If master batches of rubber and ethylidene-aniline are made, extra time, labor. and power are required and this'is obviated by use of the formaldehyde resini'fied material which may be milled into each batch of rubber and compound directly.

Aside "from the ease of handling and mill room operation. this formaldehyde-reaction producthas other distinct advantages over the material obtained from acetaldehyde and aniline alone, in that it contains less of a product that is relatively inactive during vulcanization and which has somewhat of a. softening effect on the cured product. Rubber vulcanized with the formaldehyde-resinificd product shows a higher tensile strength at the optimum cure as well as higher ultimate tensile. A

The more beneficial effect of the formaldehyde reaction product over syrupy ethyli-V Withthe syrupy ormore viscous dene-aniline can be shown in general in a vulcanization test with the following formula I a 1 f V Parts by weight. Smoked sheet rubber 100.0

' Sulfur 3.5 Zinc oxide he 3.0.

Accelerator;

Table 1 below indicates the tensile strength and ultimate elongation obtained. on cures made simultaneously on the two samples at fifteen minute intervals from fifteen minutes .to one hour andthirty minute's. Each ten- .sile and elongation figure represents the average of four tests. Column I represents Table Time of cure in mins. at Y The stress strain data on the cure obtained in thirty minutes at 141.5 C. is shown in Table 2. The average tensile strength in poundsv per square inch on four test pieces is shown for each 100% elongation. Column I" shows the data obtained on the ethylidene- I. aniline, while column 2 represents the formaldehyde-resinified material.

Table II.

. 1 I II. Elongation 1 Tensile Tensile.

Tensile and elongation at break is shown in Table 1:; Both Table I and Table II show the superiority ofthe newmate-rial;

The process of'making the new accelera (comprises combining rubber withavulcaniz- 'ing agent .anda .niethylene-alkylidenegr 1 tors may be illustrated by the following example p V I p Sixty-six parts (by weight) of acetalde- .hyde is run slowly into ninety-three parts (by weight) of aniline in a-suitable convulcanizing the rubber mix;

tainer equipped with a cooling jacket, stirrer and condenser. The temperature ot the mixture is allowed to rise gradually by its heat of reaction to about'ZO 1C. Toward the end of the addition of acctaldehyde, a small amount of refluxing usually occurs for a short time, so that it i's neccssary that the condenser be equipped. with brine or ice water to prevent the escape of acetaldehyde. After all; the acct-aldehyde has been added and'no" more refluxing of the aldehyde occurs, the

mixture is inaintainedat %85 CQfor about two hours to insure completion of the ready tion. At this time, twentysevcn partsby weightv of formaldehyde solution (37-40%) is' added, whereupon the temperature rises about 10. It is desirable to'maintainthe temperature. above 0-,, as at lower tein peratures the product becoiness'ostifi that; difhculty is experienced in fstirri'ng. 7 After the addition of the formaldehyde, stirringis continued for about two hoursto allowfforf complete reaction after which vacu'unifisf slowly applied and. the water removed; A? i i 'ter drying, the mcltedresin isdrawn off in to .suitable containers andgallowed to cool;

whenit is ready, after grinding, for use in rubber as an acceleratoro f vulcanization. 1

It will, of course, he understood'that the, 7

process isnot limite'd tothe exactconditions 4 given in the above example 3 these conditions;

7 including tlmes, temperatures, and proper-1 H 'tlOllS otreagents, may be varied cons derablyQf without departing fronrmy' invention.

The aldehyde-amine :whi'chf 'l prefer to:

treat with formaldehyde is derived? from v I acetaldehyde and aniline, butas-I, have in' I dicated above, straight or open chain ,alde-i no i hydesj in general maybe employed, and in '7 place oflaniline there may be used other aromatic (cyclic) amines such asj thetoluidines, naphthylamines, p phenyIene-diamine; and. other 'monoand poly-amines, to all of which maybe applied the termz arylamine'.

In place'of formaldehyde, other equivalent. substances containing 7 groups may be used. v y 3 The new formaldehyde derivatives consti- -c i g part of my invention'm'aybe referred V1 to generically as methylene-alkylidene-aryl-' wer me h e e amine compounds in {which the alkylidene group contains more than onecarhon atom.

I claim r 1 I 1 A "pr0cess' of treating rubber v ,QOIYIPTISGS combining rubber with a vulcania i ing agent and a polya-ldehyde derivative of an aldehyde Q. amine reaction productand;

2. A process of treatingrubber which arylamine in which the alkylidene' group" contains more than one arbon' atomfandf vulcaniz ng the rubber'mix,

comprises combining rubber with a vulcanizing agent and a formaldehyde derivative of the condensation product of an aromatic primary amine and a straight chain aldehyde. and vulcanizing the rubber mix.

4. A process of treating rubber which comprises combining rubber with a vulcanizing agent and a formaldehyde derivative ofwthe condensation product of an aromatic primary amine and acetaldehyde, and vulcanizing the rubber mix.

5. A process of treating rubber which comprises combining rubber with a vulcanizing agent and a material obtainable by treating with formaldehyde the condensation product of one molecular proportion of treating with formaldehyde the condensation product of one molecular proportion of an aromatic primary amine and about one and one half molecular proportions of acetaldehyde, between about one-third and one molecular proportion of formaldehyde being used for each molecular proportion of the aromatic primary amine, and vulcanizing the rubber mix.

7. A rubber product derived from rubber combined with the polyaldehyde derivative of an aldehyde amine reaction product and vulcanized.

8. A rubber product derived from rubber combined with the formaldehyde derivative of the condensation product of a straight chain aldehyde and an aromatic primary amine, and vulcanized.

9. A rubber product derived from rubber combined with the formaldehyde derivative of the condensation product of acetaldehyde and aniline, and vulcanized.

10. The process of producingvulcanized rubber. which comprises heating a mixture of rubber, sulfur, with the polyaldehyde derivative of an aldehyde amine reaction product. 1

11. The process of producing vulcanized rubber, which comprises heating a mixture of rubber and sulfur with a formaldehyde derivative of a compound formed by the union of three molecular pro ortions of acetaldehyde with two molecu ar proportions of aniline.

In testimony whereof I affix my signature.

WINFIELD SCOTT. 

